• C. M. Palomares Garcia, A. Di Bernardo, G. Kimbell, M. E. Vickers, F. C-P. Massabuau, S. Komori, G. Divitini, Y. Yasui, H. Gyeol Lee, J. Kim, B. Kim, M. G. Blamire, A. Vecchione, R. Fittipaldi, Y. Maeno, T. Won Noh, and J. W. A. Robinson, “Pair suppression caused by mosaic-twist defects in superconducting Sr2RuO4 thin-films prepared using pulsed laser deposition,” Communications Materials, vol. 1, 2020. doi:10.1038/s43246-020-0026-1
    [BibTeX] [Abstract] [Download PDF]

    Sr2RuO4 is a prototypical unconventional superconductor, but the superconducting symmetries of the bulk and surface states in single crystals remains controversial. Solving this problem is impeded by the challenge of producing thin-films of Sr2RuO4 free of defects and impurities which annihilate the superconductivity. Here, we report the reliable growth of superconducting Sr2RuO4 thin-films by pulsed laser deposition and identify the universal material properties that are destructive to the superconducting state. We demonstrate that careful control of the starting material is essential to achieve superconductivity as well as the use of a single crystal target of Sr3Ru2O7. By systematically varying the Sr2RuO4 film thickness, we identify mosaic twist as the key in-plane defect that suppresses superconductivity. These results are central to the development of our understanding of unconventional superconductivity.

    @article{strathprints71930,
    volume = {1},
    month = {May},
    title = {Pair suppression caused by mosaic-twist defects in superconducting Sr2RuO4 thin-films prepared using pulsed laser deposition},
    year = {2020},
    doi = {10.1038/s43246-020-0026-1},
    journal = {Communications Materials},
    keywords = {superconductor, Sr2RuO4, thin film, Physics, Atomic and Molecular Physics, and Optics},
    url = {https://doi.org/10.1038/s43246-020-0026-1},
    issn = {2662-4443},
    abstract = {Sr2RuO4 is a prototypical unconventional superconductor, but the superconducting symmetries of the bulk and surface states in single crystals remains controversial. Solving this problem is impeded by the challenge of producing thin-films of Sr2RuO4 free of defects and impurities which annihilate the superconductivity. Here, we report the reliable growth of superconducting Sr2RuO4 thin-films by pulsed laser deposition and identify the universal material properties that are destructive to the superconducting state. We demonstrate that careful control of the starting material is essential to achieve superconductivity as well as the use of a single crystal target of Sr3Ru2O7. By systematically varying the Sr2RuO4 film thickness, we identify mosaic twist as the key in-plane defect that suppresses superconductivity. These results are central to the development of our understanding of unconventional superconductivity.},
    author = {Palomares Garcia, Carla Maria and Di Bernardo, Angelo and Kimbell, Graham and Vickers, Mary E. and Massabuau, Fabien C-P. and Komori, Sachio and Divitini, Giorgio and Yasui, Yuuki and Gyeol Lee, Han and Kim, Jinkwon and Kim, Bongju and Blamire, Mark G. and Vecchione, Antonio and Fittipaldi, Rosalba and Maeno, Yoshiteru and Won Noh, Tae and Robinson, Jason W. A.}
    }

  • I. Ahmed, J. A. Haigh, S. Schaal, S. Barraud, Y. Zhu, C. Lee, M. Amado, J. W. A. Robinson, A. Rossi, J. J. L. Morton, and F. M. Gonzalez-Zalba, “Radio-frequency capacitive gate-based sensing,” Physical Review Applied, vol. 10, iss. 1, 2018. doi:10.1103/PhysRevApplied.10.014018
    [BibTeX] [Abstract] [Download PDF]

    Developing fast, accurate, and scalable techniques for quantum-state readout is an active area in semiconductor-based quantum computing. Here, we present results on dispersive sensing of silicon corner state quantum dots coupled to lumped-element electrical resonators via the gate. The gate capacitance of the quantum device is placed in parallel with a superconducting spiral inductor resulting in resonators with loaded Q factors in the 400-800 range. We utilize resonators operating at 330 and 616 MHz, and achieve charge sensitivities of 7.7 and 1.3{\ensuremath{\mu}}e/Hz, respectively. We perform a parametric study of the resonator to reveal its optimal operation points and perform a circuit analysis to determine the best resonator design. The results place gate-based sensing on a par with the best reported radio-frequency single-electron transistor sensitivities while providing a fast and compact method for quantum-state readout.

    @article{strathprints68587,
    volume = {10},
    number = {1},
    month = {July},
    title = {Radio-frequency capacitive gate-based sensing},
    year = {2018},
    doi = {10.1103/PhysRevApplied.10.014018},
    journal = {Physical Review Applied},
    keywords = {quantum computation, quantum information architectures \& platforms, quantum information with solid state qubits, radio frequency techniques, Physics, Physics and Astronomy(all)},
    url = {https://doi.org/10.1103/PhysRevApplied.10.014018},
    issn = {2331-7019},
    abstract = {Developing fast, accurate, and scalable techniques for quantum-state readout is an active area in semiconductor-based quantum computing. Here, we present results on dispersive sensing of silicon corner state quantum dots coupled to lumped-element electrical resonators via the gate. The gate capacitance of the quantum device is placed in parallel with a superconducting spiral inductor resulting in resonators with loaded Q factors in the 400-800 range. We utilize resonators operating at 330 and 616 MHz, and achieve charge sensitivities of 7.7 and 1.3{\ensuremath{\mu}}e/Hz, respectively. We perform a parametric study of the resonator to reveal its optimal operation points and perform a circuit analysis to determine the best resonator design. The results place gate-based sensing on a par with the best reported radio-frequency single-electron transistor sensitivities while providing a fast and compact method for quantum-state readout.},
    author = {Ahmed, Imtiaz and Haigh, James A. and Schaal, Simon and Barraud, Sylvain and Zhu, Yi and Lee, Chang-min and Amado, Mario and Robinson, Jason W. A. and Rossi, Alessandro and Morton, John J. L. and Gonzalez-Zalba, M. Fernando}
    }

  • A. F. Jarjour, A. M. Green, T. J. Parker, R. A. Taylor, R. A. Oliver, G. A. D. Briggs, M. J. Kappers, C. J. Humphreys, R. W. Martin, and I. M. Watson, “Two-photon absorption from single InGaN/GaN quantum dots,” Physica E: Low-dimensional Systems and Nanostructures, vol. 32, iss. 1-2, p. 119–122, 2006.
    [BibTeX] [Abstract] [Download PDF]

    We present a study of the time-integrated and time-resolved photoluminescence properties of single-InGaN/GaN quantum dots (QDs) using two-photon spectroscopy. Two samples containing QDs produced by different growth techniques are examined. We find that two-photon excitation results in the suppression of the emission from the underlying quantum well to which the QDs are coupled and yet relatively strong QD emission is observed. This effect is explained in terms of the enhancement of two-photon absorption in QDs due to the full confinement of carriers. Furthermore, evidence of the presence of excited states is revealed from the two-photon photoluminescence excitation spectra presented in the study.

    @article{strathprints10020,
    volume = {32},
    number = {1-2},
    title = {Two-photon absorption from single InGaN/GaN quantum dots},
    author = {A.F. Jarjour and A.M. Green and T.J. Parker and R.A. Taylor and R.A. Oliver and G.A.D. Briggs and M.J. Kappers and C.J. Humphreys and R.W. Martin and I.M. Watson},
    year = {2006},
    pages = {119--122},
    journal = {Physica E: Low-dimensional Systems and Nanostructures},
    keywords = {InGaN, quantum dot, two-photon absorption, photoluminescence, time-resolved, photoluminescence excitation, Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/10020/},
    abstract = {We present a study of the time-integrated and time-resolved photoluminescence properties of single-InGaN/GaN quantum dots (QDs) using two-photon spectroscopy. Two samples containing QDs produced by different growth techniques are examined. We find that two-photon excitation results in the suppression of the emission from the underlying quantum well to which the QDs are coupled and yet relatively strong QD emission is observed. This effect is explained in terms of the enhancement of two-photon absorption in QDs due to the full confinement of carriers. Furthermore, evidence of the presence of excited states is revealed from the two-photon photoluminescence excitation spectra presented in the study.}
    }

  • A. F. Jarjour, R. A. Taylor, R. W. Martin, and I. M. Watson, “Two-photon absorption in site-controlled InGaN/GaN quantum dots,” Physica Status Solidi C, vol. 2, iss. 11, p. 3843–3846, 2005.
    [BibTeX] [Abstract] [Download PDF]

    We present micro-photoluminescence measurements on single site-controlled InGaN/GaN quantum dots using two-photon excitation Furthermore, measurements of photoluminescence excitation and time-resolved photoluminescence are also presented. We show that two-photon excitation results in total suppression of the emission from the underlying quantum well, to which the quantum dots are couple, and yet strong quantum dot emission. We attribute this effect to the enhancement of the two-photon absorption in the quantum dots as a result of the zero-dimensional confinement compared to that of the quantum wells.

    @article{strathprints9983,
    volume = {2},
    number = {11},
    month = {November},
    author = {A.F. Jarjour and R.A. Taylor and R.W. Martin and I.M. Watson},
    title = {Two-photon absorption in site-controlled InGaN/GaN quantum dots},
    journal = {Physica Status Solidi C},
    pages = {3843--3846},
    year = {2005},
    keywords = {42.65.?k, 78.67.Hc, 78.47.+p;78.55.Cr, Physics, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/9983/},
    abstract = {We present micro-photoluminescence measurements on single site-controlled InGaN/GaN quantum dots using two-photon excitation Furthermore, measurements of photoluminescence excitation and time-resolved photoluminescence are also presented. We show that two-photon excitation results in total suppression of the emission from the underlying quantum well, to which the quantum dots are couple, and yet strong quantum dot emission. We attribute this effect to the enhancement of the two-photon absorption in the quantum dots as a result of the zero-dimensional confinement compared to that of the quantum wells.}
    }

  • R. W. Martin, P. R. Edwards, R. A. Taylor, J. H. Rice, J. H. Na, J. W. Robinson, J. D. Smith, C. Liu, and I. M. Watson, “Luminescence properties of isolated InGaN/GaN quantum dots,” Physica Status Solidi A – Applications and Materials Science, vol. 202, iss. 3, p. 372–376, 2005.
    [BibTeX] [Abstract] [Download PDF]

    InxGa1?xN quantum dots have been fabricated by the selective growth of GaN micro-pyramid arrays topped with InGaN/GaN quantum wells. The spatially- and spectrally-resolved luminescence properties of these structures were measured using low-temperature micro-photoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit linewidths down to 650 {\ensuremath{\mu}}eV (limited by the spectrometer resolution). We describe the broadening of the luminescence peak from a single dot as a function of temperature and excitation power.

    @article{strathprints10018,
    volume = {202},
    number = {3},
    month = {February},
    author = {R.W. Martin and P.R. Edwards and R.A. Taylor and J.H. Rice and J.H. Na and J.W. Robinson and J.D. Smith and C. Liu and I.M. Watson},
    title = {Luminescence properties of isolated InGaN/GaN quantum dots},
    journal = {Physica Status Solidi A - Applications and Materials Science},
    pages = {372--376},
    year = {2005},
    keywords = {physics, Physics, Electronic, Optical and Magnetic Materials, Condensed Matter Physics},
    url = {http://strathprints.strath.ac.uk/10018/},
    abstract = {InxGa1?xN quantum dots have been fabricated by the selective growth of GaN micro-pyramid arrays topped with InGaN/GaN quantum wells. The spatially- and spectrally-resolved luminescence properties of these structures were measured using low-temperature micro-photoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit linewidths down to 650 {\ensuremath{\mu}}eV (limited by the spectrometer resolution). We describe the broadening of the luminescence peak from a single dot as a function of temperature and excitation power.}
    }

  • P. R. Edwards, R. W. Martin, I. M. Watson, C. Liu, R. A. Taylor, J. H. Rice, J. H. Na, J. W. Robinson, and J. D. Smith, “Quantum dot emission from site-controlled InGaN/GaN micropyramid arrays,” Applied Physics Letters, vol. 85, iss. 19, p. 4281–4283, 2004.
    [BibTeX] [Abstract] [Download PDF]

    InxGa1?xN quantum dots have been fabricated by the selective growth of GaN micropyramid arrays topped with InGaN/GaN quantum wells. The spatially, spectrally, and time-resolved emission properties of these structures were measured using cathodoluminescence hyperspectral imaging and low-temperature microphotoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit decay lifetimes of approximately 0.5 ns, with linewidths down to 650 meV

    @article{strathprints3003,
    volume = {85},
    number = {19},
    month = {November},
    author = {P.R. Edwards and R.W. Martin and I.M. Watson and C. Liu and R.A. Taylor and J.H. Rice and J.H. Na and J.W. Robinson and J.D. Smith},
    title = {Quantum dot emission from site-controlled InGaN/GaN micropyramid arrays},
    journal = {Applied Physics Letters},
    pages = {4281--4283},
    year = {2004},
    keywords = {quantum dot emission, InGaN/GaN micropyramid arrays, nanoscience, Solid state physics. Nanoscience, Physics and Astronomy (miscellaneous)},
    url = {http://strathprints.strath.ac.uk/3003/},
    abstract = {InxGa1?xN quantum dots have been fabricated by the selective growth of GaN micropyramid arrays topped with InGaN/GaN quantum wells. The spatially, spectrally, and time-resolved emission properties of these structures were measured using cathodoluminescence hyperspectral imaging and low-temperature microphotoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit decay lifetimes of approximately 0.5 ns, with linewidths down to 650 meV}
    }